yet another try -- use powershell version for removing dir #313

Job	Run time
l10n	25s
zip up the rules directory	1m 10s
Build linux pyd file (64-bit intel)	2m 5s
Build 32 and 64 bit windows pyd file	3m 43s
build-addon	-1s
Pre Release	0s
	7m 22s

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